Method for selective production of racemic metallocene complexes

ABSTRACT

Racemic metallocene complexes are prepared by reacting bridged or unbridged transition metal complexes with cyclopentadienyl derivatives of alkali metals or alkaline earth metals and, if desired, subsequently replacing the aromatic ligands.

The present invention relates to a process for preparing racemic metallocene complexes by reacting bridged or unbridged aromatic transition metal complexes of the formula I

where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and the lanthanides,

X are identical or different and are each fluorine, chlorine, bromine, iodine, hydrogen C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, —OR¹⁰ or —NR¹⁰R¹¹,

n is an integer from 1 to 4, where n corresponds to the valence of M minus 2,

R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms,

R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

R¹⁰, R¹¹ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical,

Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹²,

where

R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring,

M¹ is silicon, germanium or tin and

m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where

R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

with cyclopentadienyl derivatives of alkali metals or alkaline earth metals and, if desired, subsequently replacing the bridged aromatic ligand or the two unbridged aromatic ligands; racemic metallocene complexes of the formula III

where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and of the lanthanides,

where:

R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms,

R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms and the radicals mentioned may be fully or partially substituted by heteroatoms,

Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹²,

where

R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring,

M¹ is silicon, germanium or tin and

m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where

R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

R¹³ to R¹⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R¹⁸)₃ where

R¹⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

where the radicals

R¹⁹ to R²³ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R²⁴)₃ where

R²⁴ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

or where the radicals

R¹⁶ and Z together form a group —[T(R²⁵)(R²⁶)]_(q)—E—, where

T can be identical or different and are each silicon, germanium, tin or carbon,

R²⁵, R²⁶ are each hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl

q is 1, 2, 3 or 4,

E is

or A, where A is —O—,

where

R²⁷ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl, alkylaryl or Si(R²⁸)₃

where

R²⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl or alkylaryl

and the use of racemic metallocene complexes of the formula III as catalysts or as constituents of catalysts for the polymerization of olefinically unsaturated compounds or as reagents or as catalysts in stereoselective synthesis.

Apart from stereospecific olefin polymerization, enantioselective organic synthesis is increasingly providing interesting possibilities for using chiral metallocene complexes of metals of transition groups III-VI of the Periodic Table of the Elements. As an example, mention may be made here of enantioselective hydrogenations of prochiral substrates, for example prochiral olefins as described in R. Waymouth, P. Pino, J. Am. Chem. Soc. 112 (1990), pp. 4911-4914, or prochiral ketones, imines and oximes as described in WO 92/9545.

Furthermore, mention may be made of the preparation of optically active alkenes by enantioselective oligomerization as described in W. Kaminsky et al., Angew. Chem. 101 (1989), pp. 1304-1306, and enantioselective cyclopolymerization of 1,5-hexadienes as described in R. Waymouth, G. Coates, J. Am. Chem. Soc. 113 (1991), pp. 6270-6271.

The applications mentioned generally require the use of a metallocene complex in its racemic form, ie. without meso compounds. In the case of the diastereomer mixture (rac. and meso form) obtained in the metallocene synthesis of the prior art, the meso form has to be separated off first. Since the meso form has to be discarded, the yield of racemic metallocene complex is low.

It is an object of the present invention to find a process or the selective preparation of racemic, virtually (to the accuracy of NMR measurement) meso-free metallocene complexes.

A further object is to find racemic metallocene complexes which can either be used directly as or in catalysts, primarily for olefin polymerization, or which after modification, for example after substitution by an “auxiliary ligand”, can be used as or in catalysts, primarily for olefin polymerization, or which can be used as reagents or catalysts in stereoselective synthesis.

We have found that these objects are achieved by the process defined in the claims, the racemic metallocene complexes III and their use as catalysts or in catalysts for the polymerization of olefinically unsaturated compounds or as reagents or catalysts in stereoselective synthesis.

The terms “meso form”, “racemate”, and thus also “enantiomers” in relation to metallocene complexes are known and defined, for example, in Rheingold et al., Organometallics 11 (1992), pp. 1869-1876.

For the purposes of the present invention, the term “virtualy meso-free” means that at least 90% of a compound is present in the form of the racemate.

The bridged or unbridged aromatic transition metal complexes of the present invention have the formula I

where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and the lanthanides,

X are identical or different and are each fluorine, chlorine, bromine, iodine, hydrogen C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, —OR¹⁰ or —NR¹⁰R¹¹,

n is an integer from 1 to 4, where n corresponds to the valence of M minus 2,

R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms,

R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

R¹⁰, R¹¹ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical,

Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹²,

where

R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring,

M¹ is silicon, germanium or tin and

m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where

R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

Preferred metals M are titanium, zirconium and hafnium, in particular zirconium.

Well suited substituents X are fluorine, chlorine, bromine, iodine, preferably chlorine, also C₁-C₆-alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, i-butyl or preferably tert-butyl. Also well suited as substituents X are alkoxides —OR¹⁰ or amides —NR¹⁰R¹¹ where R¹⁰ or R¹¹ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical. Such radicals X are, for example, methyl, ethyl, i-propyl, tert-butyl, phenyl, naphthyl, p-tolyl, benzyl, trifluoromethyl, pentafluorophenyl.

The substituents R¹ and R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical as substituent, e.g. methyl, ethyl or propyl. Examples of such cycloalkyl radicals are cyclopropyl, cyclopentyl, preferably cyclohexyl, norbornyl. The substituents R¹ and R⁸ may also be C₆-C₁₅-aryl such as phenyl, naphthyl; alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. p-tolyl; arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. benzyl or neophyl, or they are triorganosilyl such as Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, for example trimethylsilyl, tert-butyldimethylsilyl, triphenylsilyl. The radicals mentioned can, of course, also be partially or fully substituted by heteroatoms, for example by S—, N—, O—, or halogen-containing structural elements. Examples of such substituted radicals R¹ and R⁸ are trifluoromethyl, pentafluoroethyl, heptafluoropropyl, heptafluoroisopropyl, pentafluorophenyl.

Preferred substituents R¹ and R⁸ are those which take up a lot of space. Such substituents are usually called bulky substituents. They are distinguished by the fact that they can cause steric hindrance.

In general, these groups are organic or organosilicon radicals which take up a lot of space (bulky radicals), but also fluorine and preferably chlorine, bromine and iodine. The number of carbon atoms in such organic or organosilicon radicals is usually not less than three.

Preferred non-aromatic, bulky radicals are those organic or organosilicon radicals which are branched in the α position or a higher position. Examples of such radicals are branched C₃-C₂₀-aliphatic, C₉-C₂₀-araliphatic and C₃-C₁₀-cycloaliphatic radicals, e.g. iso-propyl, tert-butyl, iso-butyl, neo-pentyl, 2-methyl-2-phenylpropyl (neophyl), cyclohexyl, 1-methylcyclohexyl, bicyclo[2.2.1]hept-2-yl (2-norbornyl), bicyclo[2.2.1]hept-1-yl (1-norbornyl), adamantyl. Further possible radicals of this type are organosilicon radicals having from three to thirty carbon atoms, for example trimethylsilyl, triethylsilyl, triphenylsilyl, tert-butyldimethylsilyl, tritolylsilyl or bis(trimethylsilyl)methyl.

Preferred aromatic, bulky groups are, as a rule, C₆-C₂₀-aryl radicals such as phenyl, 1- or 2-naphthyl or preferably C₁-C₁₀-alkyl- or C₃-C₁₀-cycloalkyl-substituted aromatic radicals such as 2,6-dimethylphenyl, 2,6-di-tert-butylphenyl, mesityl.

Very particularly preferred substituents R¹ and R⁸ are i-propyl, tert-butyl, trimethylsilyl, cyclohexyl, i-butyl, trifluoromethyl, 3,5-dimethylphenyl.

In the preferred substitution pattern, R¹ and R⁸ in formula I are identical.

The substituents R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical such as methyl, ethyl or propyl as substituent. Examples of such cycloalkyl radicals are cyclopropyl, cyclopentyl, preferably cyclohexyl, norbornyl. Furthermore, the substituents R² to R⁷ may be C₆-C₁₅-aryl, such as phenyl or naphthyl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. p-tolyl, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. benzyl or neophyl, or they are triorganosilyl such as Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl, for example trimethylsilyl, tert-butyldimethylsilyl, triphenylsilyl. However, the radicals R² to R⁷ can also be connected to one another in such a way that adjacent radicals form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms. Preferably, the radicals R³ and R⁴ and/or the radicals R⁵ and R⁶ are connected via a C₂-bridge in such a way that a benzo-fused ring system (naphthyl derivative) is formed. The radicals R² to R⁷ can, of course, also be partially or fully substituted by heteroatoms, for example by S—, N—, O—, or halogen-containing structural elements. Examples of such substituted radicals R² to R⁷ are trifluoromethyl, pentafluoroethyl, heptafluoropropyl, heptafluoroisopropyl, pentafluorophenyl.

Particularly preferably, the radicals R² and R⁷ are identical and are each hydrogen and R³, R⁴, R⁵ and R⁶ are as defined above.

Suitable bridging units Y, Y¹ are the following:

═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹²,

where

R¹² are identical or different and are each a hydrogen atom, a halogen atom, a C₁-C₁₀-alkyl group, a C₁-C₁₀-fluoroalkyl group, a C₆-C₁₀-fluoroaryl group, a C₆-C₁₀-aryl group, a C₁-C₁₀-alkoxy group, a C₂-C₁₀-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₈-C₄₀-arylalkenyl group or a C₇-C₄₀-alkylaryl group or R¹² and R¹³ or R¹² and R¹⁴, in each case together with the atoms connecting them, form a ring,

M¹ is silicon, germanium or tin.

Preferred bridging units Y, Y¹ are methylene —CH₂—, S, O, —C(CH₃)2—, where m in formula I is preferably 1 or 2; Y¹ are very particularly preferably identical and are each oxygen —O—. Very particular preference is given to phenoxide-type structures in which m in the formula I is zero, ie. the aromatic ring systems are linked directly to one another, for example to form a biphenyl derivative.

Among the unbridged aromatic transition metal complexes of the present invention of the formula I, preference is given to those in which Y represent radicals R′ and R″ which are identical or different and are fluorine, chlorine, bromide, iodine, C₁-C₂₀-alkyl or 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical such as methyl, ethyl or propyl. Examples of such cycloalkyl radicals are cyclopropyl, cyclopentyl, preferably cyclohexyl, norbornyl. Further possible meanings of the substituents R′ and R″ are C₆-C₁₅-aryl such as phenyl or naphthyl; alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. p-tolyl; arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, e.g. benzyl or neophyl, or triorganosilyl such as Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl, for example trimethylsilyl, tert-butyldimethylsilyl or triphenylsilyl. The radicals mentioned can of course also be fully or partially substituted by heteroatoms, for example by structural elements containing S, N, O or halogen atoms. Examples of such substituted radicals R′ and R″ are the trifluoromethyl, pentafluoroethyl, heptafluoropropyl, heptafluoroisopropyl and pentafluorophenyl groups.

R′ and R″ are particularly preferably identical. Very particularly preferred unbridged aromatic transition metal complexes are ones in which R¹, R⁸, R′ and R″ are identical.

The bridged or unbridged aromatic transition metal complexes I are generally prepared by methods with which those skilled in the art are familiar.

The synthesis of bridged transition metal phenoxide complexes is described for example in C. J. Schaverien, J. Am. Chem. Soc. (1995), pages 3008 to 3012. It has been found to be useful to employ the following procedure, which is generally carried out at from 0 to 80° C., preferably at first at about 20° C., and the reaction is then completed by boiling under reflux. The biphenol is first deprotonated in a solvent, for example tetrahydrofuran (THF), for example using sodium hydride or n-butyllithium, and the transition metal compound, for example the halide such as titanium tetrachloride, zirconium tetrachloride or hafnium tetrachloride, advantageously in the form of the bis-THF adducts, is subsequently added. After the reaction is complete, the product is generally obtained by crystallization after removal of salts. Unbridged transition metal phenoxide complexes can be prepared, for example, as described by H. Yasuda et al., J. Organomet. Chem. 473 (1994), pages 105 to 116.

The bridged or unbridged aromatic transition metal complexes I of the present invention generally still contain from 2 to 4 equivalents of a Lewis base which is generally introduced as a result of the synthetic route. Examples of such Lewis bases are ethers such as diethyl ether or tetrahydrofuran (THF). It is, however, also possible to obtain the aromatic transition metal complexes free of Lewis bases, for example by drying under reduced pressure or by selecting other solvents in the synthesis. Such measures are known to those skilled in the art.

The racemic metallocene complexes of the present invention are prepared by reacting the bridged or unbridged aromatic transition metal complexes I with cyclopentadienyl derivatives of the alkali metals or alkaline earth metals. Preference is given to using aromatic transition metal complexes I in which M is zirconium and the radicals R¹ and R⁸ have the preferred meanings described above. Very useful aromatic transition metal complexes I are dichlorobis(6-tert-butyl-4-methylphenoxy)zirconium.(THF)₂ and the zirconium phenoxide compounds mentioned in the examples.

In principle, suitable cyclopentadienyl derivatives of the alkali metals or alkaline earth metals are those which, after reaction with the bridged aromatic transition metal complexes I of the present invention, selectively give virtually meso-free, racemic metallocene complexes.

The racemic metallocene complexes of the present invention may be bridged, but do not have to be. In general, a high barrier to rotation, in particular in the temperature range from 20 to 80° C., (which can be determined by ¹H and/or ¹³C-NMR-spectroscopy) of the unbridged cyclopentadienyl-type ligands in the metallocene is sufficient to enable the metallocene complexes to be isolated directly in their racemic form without them being able to transform into the meso form. The barrier to rotation necessary to ensure this is usually above 20 kJ/mol.

Well suited cyclopentadiene derivatives of alkali metals or alkaline earth metals are those of the formula II

where the substituents and indices have the following meanings:

M² is Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba,

R¹³ to R¹⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R¹⁸)₃ where

R¹⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

where the radicals

R¹⁹ to R²³ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R²⁴)₃ where

R²⁴ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

or where the radicals

R¹⁶ and Z together form a group —[T(R²⁵)(R²⁶)]_(n)—E— where

T can be identical or different and are each silicon, germanium, tin or carbon,

R²⁵, R²⁶ are each hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl

n is 1, 2, 3 or 4,

E is

or A, where

A is —O—,

where

R²⁷ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl, alkylaryl or Si(R²⁸)₃

where

R²⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl or alkylaryl,

where

p═1 for Be, Mg, Ca, Sr, Ba and

p═2 for Li, Na, K, Rb, Cs.

Preferred compounds of the formula II are those in which M² is lithium, sodium and in particular magnesium. Furthermore, particular preference is given to those compounds of the formula II a)

in which M² is magnesium, R¹⁷ and R²³ are substituents different from hydrogen, e.g. C₁-C₁₀-alkyl, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, i-butyl or hexyl, also C₆-C₁₀-aryl, such as phenyl or trialkylsilyl, such as trimethylsilyl, T(R²⁵R²⁶) is bis-C₁-C₁₀-alkylsilyl or bis-C₆-C₁₀-arylsilyl, e.g. dimethylsilyl, diphenylsilyl, also 1,2-ethanediyl or methylene and the radicals R¹³ to R¹⁵ and R¹⁹ to R²⁵ are as defined above and, in particular, form an indenyl-type ring system or a benzindenyl-type ring system.

Very particularly preferred compounds II are those which are described in the examples and additionally

dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)magnesium

diethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)magnesium

dimethylsilanediylbis(3-tert-butyl-5-ethylcyclopentadienyl)magnesium

dimethylsilanediylbis(3-tert-pentyl-5-methylcyclopentadienyl)magnesium

dimethylsilanediylbis(2,4,7-trimethylindenyl)magnesium

1,2-ethanediylbis(1-{2,4,7-trimethylindenyl)}magnesium

dimethylsilanediylbis(1-indenyl)magnesium

dimethylsilanediylbis(4,5,6,7-tetrahydro-1-indenyl)magnesium

dimethylsilanediylbis(2-methylindenyl)magnesium

phenyl(methyl)silanediylbis(2-methylindenyl)magnesium

diphenylsilanediylbis(2-methylindenyl)magnesium

dimethylsilanediylbis(2-methyl-4,5,6,7-tetrahydro-1-indenyl)magnesium

dimethylsilanediylbis(2,4-dimethyl-6-isopropylindenyl)magnesium

dimethylsilanediylbis(2-methyl-1-benzindenyl)magnesium

dimethylsilanediylbis(2-ethyl-1-benzindenyl)magnesium

dimethylsilanediylbis(2-propyl-1-benzindenyl)magnesium

dimethylsilanediylbis(2-phenyl-1-benzindenyl)magnesium

diphenylsilanediylbis(2-methyl-1-benzindenyl)magnesium

phenylmethylsilanediylbis(2-methyl-1-benzindenyl)magnesium

ethanediylbis(2-methyl-1-benzindenyl)magnesium

dimethylsilanediylbis(2-methyl-1-tetrahydrobenzindenyl)magnesium

dimethylsilanediylbis(2-methyl-4-isopropyl-1-indenyl)magnesium

dimethylsilanediylbis(2-methyl-4-phenyl-1-indenyl)magnesium

dimethylsilanediylbis(2-methyl-4-naphthyl-1-indenyl)magnesium

dimethylsilanediylbis(2-methyl-4-{3,5-trifluoromethyl}phenyl-1-indenyl)magnesium

dimethylsilanediylbis(2-ethyl-4-isopropyl-1-indenyl)magnesium

dimethylsilanediylbis(2-ethyl-4-phenyl-1-indenyl)magnesium

dimethylsilanediylbis(2-ethyl-4-naphthyl-1-indenyl)magnesium

dimethylsilanediylbis(2-ethyl-4-{3,5-trifluoromethyl}phenyl-1-indenyl)magnesium

ethanediylbis(2-methyl-4-phenyl-1-indenyl)magnesium

ethanediylbis(2-methyl-4-naphthyl-1-indenyl)magnesium

ethanediylbis(2-methyl-4-{3,5-di-(trifluoromethyl)}phenyl-1-indenyl)magnesium

Such alkali metal or alkaline earth metal compounds II can be obtained by literature methods, for example by the, preferably stoichiometric, reaction of an organometallic compound or a hydride of the alkali or alkaline earth metal with the corresponding cyclopentadienyl-type hydrocarbons. Suitable organometallic compounds are, for example, n-butyllithium or di-n-butylmagnesium.

The reaction of the bridged or unbridged aromatic transition metal complexes I with the cyclopentadienyl derivatives of alkali or alkaline earth metals, preferably of the formula II or IIa), is usually carried out in an organic solvent or suspension medium, preferably in an ether such as diethyl ether, THF and at from −78 to 100° C., preferably at from 0 to 60° C. The molar ratio of the aromatic transition metal complex I to the cyclopentadienyl derivative of alkali or alkaline earth metals is usually in the range from 0.8:1 to 1:1.2, preferably 1:1.

The racemic metallocene complexes of the present invention are preferably those of the formula III

where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and the lanthanides,

where:

R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms,

R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms and the radicals mentioned may be fully or partially substituted by heteroatoms,

Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹²,

where

R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring,

M¹ is silicon, germanium or tin and

m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where

R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms,

R¹³ to R¹⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R¹⁸)₃ where

R¹⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

where the radicals

R¹⁹ to R²³ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R²⁴)₃ where

R²⁴ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

or where the radicals

R¹⁶ and Z together form a group —[T(R²⁵)(R²⁶)]_(q)—E—, where

T can be identical or different and are each silicon, germanium, tin or carbon,

R²⁵, R²⁶ are each hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl

q is 1, 2, 3 or 4,

E is

or A, where

A is —O—,

where

R²⁷ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl, alkylaryl or Si(R²⁸)₃

where

R²⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl or alkylaryl.

Preferred compounds of the formula III are those in which M is titanium, hafnium or, in particular, zirconium. Furthermore, particular preference is given to bridged compounds of the formula III (ansa-metallocenes) in which R¹⁷ and R²³ are substituents different from hydrogen, e.g. C₁-C₁₀-alkyl, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, i-butyl, hexyl, also C₆-C₁₀-aryl, such as phenyl or trialkylsilyl, such as trimethylsilyl, T(R²⁵R²⁶) is bis-C₁-C₁₀-alkylsilyl or bis-C₆-C₁₀-arylsilyl, e.g. dimethylsilyl, diphenylsilyl, also 1,2-ethanediyl, methylene and the radicals R¹³ to R¹⁵ and R¹⁹ to R²⁵ are as defined above and, in particular, form an indenyl-type ring system or a benzindenyl-type ring system.

Very particularly preferred compounds III are those which are described in the examples and additionally

dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

diethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(3-tert-butyl-5-ethylcyclopentadienyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(3-tert-pentyl-5-methylcyclopentadienyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2,4,7-trimethylindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

1,2-ethanediylbis(1-{2,4,7-trimethylindenyl)}[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(4,5,6,7-tetrahydro-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methylindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

phenyl(methyl)silanediylbis(2-methylindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

diphenylsilanediylbis(2-methylindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-4,5,6,7-tetrahydro-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2,4-dimethyl-6-isopropylindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-ethyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-propyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-phenyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

diphenylsilanediylbis(2-methyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

phenylmethylsilanediylbis(2-methyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

ethanediylbis(2-methyl-1-benzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-1-tetrahydrobenzindenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-4-isopropyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-4-phenyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-4-naphthyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-methyl-4-{3,5-trifluoromethyl}phenyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-ethyl-4-isopropyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-ethyl-4-phenyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-ethyl-4-naphthyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

dimethylsilanediylbis(2-ethyl-4-{3,5-trifluoromethyl}phenyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

ethanediylbis(2-methyl-4-phenyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

ethanediylbis(2-methyl-4-naphthyl-1-indenyl)[bis(6-tert-butyl-4-methylphenoxy)]zirconium

ethanediylbis(2-methyl-4-{3,5-di-(trifluoromethyl)}phenyl-1-indenyl)zirconium

The racemic metallocene complexes, preferably those of the formula III, can generally be modified further.

In particular, a bridged bisphenoxide ligand X¹ in the complex III can, for example, be split off (replaced) and reused. Suitable replacement methods are reaction of the racemic metallocene complexes, preferably those of the formula III, with a Brönsted acid such as a hydrogen halide, ie. HF, HBr, HI, preferably HCl, which is generally employed as such or as a solution in water or an organic solvent such as diethyl ether, THF. This usually gives the dihalide analogous to the formula III (X=F, Cl, Br, I) and the bisphenol. Another well suited replacement method is reaction of the racemic metallocene complexes, preferably those of the formula III, with organoaluminum compounds such as tri-C₁-C₁₀-alkylaluminum, e.g. trimethylaluminum, triethylaluminum, tri-n-butylaluminum or tri-iso-butylaluminum. This generally gives, according to the present state of knowledge, the organo compound analogous to III (x=organic radical, e.g. C₁-C₁₀-alkyl, such as methyl, ethyl, n-butyl or i-butyl) and, for example, the organoaluminum binaphthoxide. An analogous method can also be employed if the ligand X¹ in the complex III consists of two unbridged phenoxide ligands.

In the cleavage reactions, the components are usually used in the stoichiometric ratio.

The stereochemistry of the metallocene complexes is generally retained during the cleavage reactions, ie. there is generally no conversion of the racemic form into the meso form of the metallocene complexes.

The process of the present invention makes it possible to obtain the racemic form of metallocene complexes very selectively. Bridged indenyl- or benzindenyl-type metallocenes which have a ligand different from hydrogen in the vicinity of the bridging unit (the 2 position) can be obtained particularly advantageously.

The racemic metallocene complexes of the present invention, in particular those of the formula III or their above-described derivatives which can be obtained, for example, by replacement of the phenoxide ligands, can be used as catalysts or in catalyst systems for the polymerization of olefinically unsaturated compounds such as ethylene, propylene, 1-butene, 1-hexene, 1-octene or styrene. Their use is particularly advantageous in the stereoselective polymerization of prochiral, olefinically unsaturated compounds such as propylene and styrene. Suitable catalysts or catalyst systems in which the racemic metallocene complexes of the present invention can function as “metallocene component” are usually obtained by means of compounds capable of forming metallocenium ions, as are described, for example, in EP-A-0 700 935, page 7, line 34 to page 8, line 21 and formulae (IV) and (V). Further compounds capable of forming metallocenium ions are aluminoxanes (RAlO)_(n) such as methylaluminoxane.

The racemic metallocene complexes of the present invention, in particular those of the formula III or their above-described derivatives which can be obtained, for example, by splitting off the phenoxide ligands, can also be used as reagents or as catalysts or in catalyst systems in stereoselective, in particular organic, synthesis. As an example, mention may be made of the stereoselective reduction or stereoselective alkylation of C═C double bonds or C═O—, C═N double bonds.

EXAMPLES ABBREVIATIONS AND ACRONYMS

Me═methyl, tBu═tert-butyl, iPr═iso-propyl

Example A

Preparation of Dichlorobis(6-t-butyl-4-methylphenoxy)zirconium-(THF)₂[p-Me-bpZrCl₂(THF)₂]

0.483 g (0.02 mol) of NaH was added a little at a time at room temperature while stirring to a solution of 3.27 g (0.01 mol) of 2,2′-dihydroxy-3,3′-di-t-butyl-5,5′-dimethylbiphenyl in 150 ml of THF, the mixture was subsequently stirred for one hour at room temperature and the suspension was then refluxed for 24 hours. After cooling the clear, slightly orange solution, 3.8 g (0.01 mol) of ZrCl₄×2THF were added a little at a time while stirring and the suspension was again refluxed for 24 hours. The NaCl formed was filtered off and the solvent was removed under reduced pressure. 100 ml of ether were added to the residue. After a short time, a white solid precipitated from the initially clear solution. To complete the crystallization, the solution was cooled to −30° C. The precipitate was filtered off and washed with a little cold ether. This gave 4.59 g (73% of theory) of dichlorobis(6-t-butyl-4-methylphenoxy)zirconium×2THF: [p-Me-bp]ZrCl₂×2THF.

¹H-NMR: (C₆D₆, 250 Mhz): 7.26 (d, 2H, C₆H₂), 7.04 (d, 2H, C₆H₂), 4.06 (b, 8H, THF), 2.21 (s, 6H, Me), 1.74 (s, 18H, t-Bu), 1.05 (b, 8H, THF)

Example 1

Preparation of Rac-C₂H₄(ind₂Zr(p-Me-bp)

a) Preparation of C₂H₄(ind)₂Mg(THF)₂

6.3 ml of dibutyl magnesium in heptane (6.3 mmol, 1 M Bu₂Mg solution) were added at room temperature to a solution of 1.49 g (5.77 mmol) of C₂H₄(indH)₂ in 150 ml of heptane. The solution was refluxed for 5 hours. This resulted in formation of a yellowish precipitate. The suspension was cooled to −30° C., the precipitate was filtered off, washed with a little heptane and dried under reduced pressure. The crude product was taken up in a little THF and covered with heptane. The C₂H₄(ind)₂Mg(THF)₂ was obtained in the form of pale violet needles. The yield was 1.86 g (76% of theory)

b) Complexation

0.459 g (1.08 mmol) of C₂H₄(ind)₂Mg(THF)₂ and 0.679 g (1.08 mmol) of p-Me-bpZrCl₂(THF)₂ were mixed dry. While stirring, 50 ml of toluene were added and the suspension was stirred for two days at room temperature. During this time, the solution became increasingly yellow-orange and became turbid. The precipitate was filtered off, the toluene was removed from the filtrate under reduced pressure and the residue was taken up in 100 ml of pentane. The slightly turbid solution was filtered through kieselguhr and the pentane was removed under reduced pressure. This gave 0.495 g (68% of theory) of rac-C₂H₄(ind)₂Zr(p-Me-bp).

¹H-NMR: (C₆D₆, 250 Mhz): 7.40 (d, 2H, ind-C₆H₄), 7.21 (d, 2H, C₆H₂), 6.9 (m, 6H, ind-C₆H₄), 6.77 (d, 2H, C₆H₂), 6.00 (d, 2H, ind-C₃H₂), 5.76 (d, 2H, ind-C₉H₂), 3.29 (m, 4H, C₂H₄), 2.18 (s, 6H, Me), 1.36 (s, 18H, t-Bu).

Example 2

Preparation of Rac-Me₂Si(2-Me-Tetrahydrobenzo[e]inden-3-yl)₂-Zr((p-Me-bp)

a) Preparation of Me₂Si(2-Me-Tetrahydrobenzo[e]inden-3-yl)₂-Mg(THF)₂

2.5 ml (2.5 mmol) of a 1 M dibutylmagnesium solution in heptane were added to a solution of 1 g (2.35 mmol) of rac-Me₂Si(2-Me-tetrahydrobenzo[e]inden-3-yl)2Mg in 100 ml of heptane. The solution was refluxed for 6 hours. After cooling to room temperature, 0.4 ml of THF was added. After a few days at room temperature, yellow-green needles of Me₂Si(2-Me-tetrahydrobenzo[e]inden-3-yl)₂Mg(THF)₂.0.5(C₇H₁₆) were isolated by decantation, washed with a little heptane and dried under reduced pressure. This gave 0.57 g (38% of theory) of the desired product.

¹H-NMR: (CH₂Cl₂, 600 Mhz): 7.53 (d, 2H, C₆H₂), 6.55 (d, 2H, C₆H₂), 6.28 (s, 2H, C₅H₁), 3.2-2.4 (m), 2.2-1.5 (m), 0.65 (d, 6H, Me₂Si)

b) Preparation of Rac-Me₂Si(2-Me-Tetrahydrobenzo[e]inden-3-yl)₂-Zr(p-Me-bp)

500 mg (0.85 mmol) of Me₂Si(2-Me-tetrahydrobenzo[e]inden-3-yl)₂-Mg(THF)₂ and 556 mg (0.85 mmol) of p-Me-bpZrCl₂(THF)₂ were mixed dry. While stirring, 60 ml of toluene were added and the suspension was stirred for two days at room temperature. During this time, the solution became increasingly yellow and became turbid. The precipitate was filtered off, the toluene was removed from the filtrate under reduced pressure and the residue was taken up in 100 ml of pentane. The slightly turbid solution was filtered and the pentane was removed under reduced pressure. This gave 0.498 g (70% of theory) of rac-Me₂Si(2-Me-tetrahydrobenzo[e]inden-3-yl)₂Zr(p-Me-bp).

¹H-NMR (₆D₆, 250 Mhz): 7.46 (d, 2H, ind-C₆H₂), 7.22 (d, 2H, C₆H₂), 6.73 (d, 2H, C₆H₂), 6.52 (d, 2H, ind-C₆H₂), 6.09 (s, 2H, C₅H₁), 2.46 (s, 6H, ind-Me), 2.21 (s, 6H, Me), 138 (s, 18H, t-Bu), 0.96 (s, 6H, Me₂Si)

Example 3

Preparation of Me₂SiCp₂Mg(THF)₂

11.21 ml (12.20 mmol) of a 1.08 m dibutylmagnesium solution in heptane were added to a solution of 2.28 g (12.10 mmol) of Me₂Si(CPH)₂ in 60 ml of heptane. This resulted in the solution becoming turbid owing to a white precipitate. The solution was refluxed for 5 hours. At room temperature, 3 ml (37 mmol) of THF were added. The solution was stirred for 1 hour at room temperature, evaporated to about 30 ml in a high vacuum and stored at −30° C. in a freezer. After a few days, the white precipitate was filtered off, washed with a little heptane and dried under reduced pressure. This gave 3.35 g (78%) of Me₂SiCp₂Mg(THF)₂.

¹H-NMR chemical shifts in ppm (CD₂Cl₂, internal standard TMS, 298 K, 250 MHz)

Assignment 6.21 tp C₅H₄ 6.09 sb C₅H₄ 3.64 m THF 1.85 m THF 0.54 s (CH₃)₂Si

Example 4

Preparation of Me₄C₂(3-^(t)Bu-Cp)₂Mg(THF)₂

23 ml (23 mmol) of a 1 M dibutylmagnesium solution in heptane were added to a solution of 6.78 g (20.76 mmol) of Me₄C₂(3-tBu-CpH)₂ in 200 ml of heptane. The solution was refluxed for 5 hours during which the evolution of butane could be observed. 4 ml of THF were added to the slightly yellowish solution and the mixture was stirred for 1 hour at room temperature, evaporated to a quarter of its value and cooled to −30° C. After a few days, colorless crystals had formed. These were separated off by decantation, washed with a little heptane and dried under reduced pressure. This gave 6.83 g (78%) of Me₄C₂(3-^(t)Bu-Cp)₂Mg(THF). Further evaporation of the mother liquor and cooling to −30° C. gave, after the same work-up, a further 0.35 g (4%) of Me₄C₂(3-^(t)Bu-Cp)₂Mg(THF).

¹H-NMR chemical shifts in ppm (CD₂Cl₂, internal standard TMS, 298 K, 600 MHz)

Assignment 5.96 (t^(p), 1H) C₅H₃ (H2) 5.56 (t^(p), 1H) C₅H₃ (H4) 5.47 (t^(p), 1H) C₅H₃ (H5) 1.54 (s, 6H) C₂(CH₃)₂(CH₃1) 1.40 (s, 6H) C₂(CH₃)₂(CH₃2) 1.16 (s, 18H) C(CH₃)₃

Example 5

Preparation of Me₂Si(ind)₂Mg(THF)₂

37 ml (37 mmol) of a 1 M dibutylmagnesium solution in heptane were added to a solution of 10.54 g (36.54 mmol) of Me₂Si(indH)₂ in 150 ml of heptane. The solution was refluxed for 8 hours while stirring vigorously. Small amounts of a precipitate were formed. 30 ml of THF (0.37 mol) were then added at room temperature while stirring vigorously. A whitish pink solid immediately precipitated. This was filtered off, washed with a little heptane and dried in a high vacuum. This gave 9.98 g (61%) of Me₂Si(ind)₂Mg(THF)₂. The filtrate was evaporated to a much smaller volume in a high vacuum and the solution was stored at −30° C. in a freezer. After a few days, a further 1.85 g (11%) of Me₂Si(ind)₂Mg(THF)₂ were obtained by an identical work-up. Total yield: 72%

¹H-NMR chemical shifts in ppm (CD₂Cl₂, internal standard TMS, 298 K, 250 MHz)

Assignment 7.96 (d, 2H) ³J (7.9 Hz) C₆H₄ 7.52 (d, 2H) ³J (7.9 Hz) C₆H₄ 6.98 (d, 2H) ³J (3.3 Hz) C₅H₂ 6.93 (t^(p), 2H) C₆H₄ 6.83 (t^(p), 2H) C₆H₄ 6.53 (d, 2H) ³J (3.1 Hz) C₅H₂ 3.03 (d, 8H) THF 1.51 (b, 8H) THF 0.94 (s, 6H) (CH₃)₂Si

Example 6

Preparation of Me₂Si(3-^(t)Bu-Cp)₂Mg(THF)₂

19.65 ml (19.65 mmol) of a 1 M dibutylmagnesium solution in heptane were added to a solution of 5.37 g (17.86 mmol) of Me₂Si(3-^(t)Bu-CpH)₂ in 200 ml of heptane. The reaction solution was refluxed for 5 hours during which the evolution of butane could be observed. The clear solution was evaporated to about one third of its volume. 3 ml (36.86 mmol) of THF were added at room temperature and the solution was cooled to −30° C. After a few days, some colorless crystals and some amorphous precipitate were formed. Both were isolated by decantation, washed with a little heptane and dried in a high vacuum. This gave 5.1 g (61%) of Me₂Si(3-^(t)Bu-Cp)₂Mg(THF)₂. Further evaporation of the mother liquor and cooling to −30° C. gave, after identical isolation, a further 2.0 g (24%) of Me₂Si(3-^(t)-Bu-Cp)₂Mg(THF)₂.

¹H-NMR chemical shifts in ppm (d⁸-THF, internal standard TMS, 298 K, 600 MHz)

Assignment 6.14 (s, 2H) C₅H₃ (H4) 6.00 (s, 2H) C₅H₃ (H2) 5.67 (s, 2H) C₅H₃ (H5) 1.16 (s, 18H) (CH₃)₃C 0.37 (b, 6H) (CH₃)₂Si

Example 7

Preparation of Me₂Si(3-(2-Me-benz[e]indenyl)₂Mg(THF)₂

3 ml (3 mmol) of a 1 M dibutylmagnesium solution were added at room temperature to a suspension of 1.09 g (2.61 mmol) of Me₂Si(3-(3H-2-Me-benz[e]indenyl)₂ in 80 ml of heptane. The suspension was heated to boiling under reflux. Shortly before the boiling point, the solution was clear. The solution became turbid after about 30 minutes as a result of precipitated product and the evolution of butane could be observed. After boiling for 12 hours, 6 ml (74 mmol) of THF were added at room temperature to the yellow suspension. The solid became brilliant yellow. After stirring for 1 hour at room temperature, the suspension was evaporated to about 20 ml in a high vacuum, the precipitate was filtered off, washed with a little heptane and dried in a high vacuum. This gave 1.29 g (85%) of Me₂Si(3-(2-Me-benz[e]indenyl)₂Mg(THF)₂.

¹H-NMR chemical shifts in ppm (C₆D₆, internal standard TMS, 298 K, 250 MHz)

Assignment 8.45 (d, 2H) C₆H₄ or C₆H₂ 8.34 (d, 2H) C₆H₄ or C₆H₂ 8.23 (d, 2H) C₆H₄ or C₆H₂ 7.82 (d, 2H) C₆H₄ or C₆H₂ 7.42 (t^(p), 2H) C₆H₄ 7.22 (t^(p), C₆D₆₎ C₆H₄ 7.14 (s, 2H) C₅H 2.95 (s, 6H) CH₃ 2.79 (b, 8H) THF 1.10 (s, 6H) (CH₃)₂Si 1.07 (b, 8H) THF

Example 8

Preparation of Rac-C₂H₄(ind)₂Zr-(2,2′-(3-Me-6-iPr-C₆H₂O)₂)

0.172 g (0.40 mmol) of 2,2′(3-^(i)Pr-5-Me-C₆H₂O)₂Zr(THF)₂ and 0.245 g (0.40 mmol) of C₂H₄(ind)₂Mg(THF)₂ were mixed dry and dissolved in 20 ml of toluene. The solution became increasingly yellow and became turbid. After stirring at room temperature for 3 hours, the solvent was removed in a high vacuum and the residue was taken up in hexane. The MgCl₂(THF)₂ was filtered off and washed with hexane. The solvent was removed in a high vacuum and the residue was taken up in 3 ml of toluene. After a few days at room temperature, pale yellow crystals were formed. These were isolated by decantation and dried in a high vacuum. This gave 0.110 g (41%) of C₂H₄(ind)₂Zr-(2,2′-(3-Me-6-iPr-C₆H₂O)₂).

¹H-NMR chemical shifts in ppm (C₆D₆, internal standard TMS, 298 K, 600 MHz)

Assignment 7.36 (d, 2H) ³J (8.5 Hz) C₆H₄ (H7) 7.15 (under C₆D₆ signal) C₆H₄ (H4) 6.94 (t^(p), 2H) C₆H₄ (H6) 6.87 (t^(p), 2H) C₆H₄ (H5) 6.80 (d, 2H) ³J (7.6 Hz) C₆H₂ (H5) 6.71 (d, 2H) ³J (8.5 Hz) C₆H₄ (H4) 5.93 (d, 2H) ³J (3.1 Hz) C₅H₂ (H2) 5.53 (d, 2H) ³J (3.0 Hz) C₅H₂ (H3) 3.23 (s, 6H) C₂H₄ 2.82 (sp, 2H) ³J (6.8 Hz) (CH₃)₂CH 1.94 (s, 6H) CH₃ 1.40 (d, 6H) ³J (7.1 Hz) (CH₃)₂CH 1.16 (d, 6H) ³J (6.6 Hz) (CH₃)₂CH

Example 9

Preparation of 2,2′-CH₂-(4-Me-6-^(t)Bu-C₆H₂O)₂ZrCl₂(THF)₂

1.44 g (60 mmol) of NaH were added a little at a time to a solution of 10.2 g (30 mmol) of 2,2′-CH₂-(4-Me-6-^(t)BUC₆H₂OH)₂ in 100 ml of THF. The suspension was subsequently refluxed for 24 hours. At room temperature, 11.3 g (30 mmol) of ZrCl₄(THF₂) were then added to the clear, orange solution and the solution was refluxed for 12 hours. The NaCl formed was filtered off, washed with THF and the solvent was removed from the filtrate in a high vacuum. 50 ml of ether were added to the foamed solid. After a short time, a white solid precipitated from the initially clear solution. This was separated off by decantation, washed with a little ether and dried in a high vacuum. This gave 12.38 g (64%) of 2,2′-CH₂-(4-Me-6-^(t)Bu-C₆H₂O)₂ZrCl₂(THF)₂. The mother liquor and the washing solution were combined, evaporated to a much smaller volume in a high vacuum and stored at −30° C. in a freezer. After a few days, the crystalline precipitate was isolated in the same way. This gave a further 2.11 g (11%) of 2,2′-CH₂-(4-Me-6-^(t)Bu-C₆H₂O)₂ZrCl₂(THF)₂. Total yield: 75%

¹H-NMR chemical shifts in ppm (CD₂Cl₂, internal standard TMS, 298 K, 250 MHz)

Assignment 7.16 (d, 2H) ⁴J (1.8 Hz) 7.27 C₆H₂ 6.96 (d, 2H) ⁴J (1.9 Hz) 7.05 C₆H₂ 5.3 (b,1H) CH₂ 4.45 (m, 8H) THF 3.33 (d, 1H) ³J (1.9 Hz) CH₂ 2.31 (s, 6H) 2.34 CH₃ 2.04 (m, 8H) THF 1.49 (s, 18H) 1.56 (CH₃)₃C

Example 10

Preparation of Rac-Me₂SiCp₂Zr(2,2′-CH₂-(4-Me-6-^(t)BuC₆H₂O)₂)

0.374 g (1.05 mmol) of Me₂SiCp₂Mg(THF)₂ and 0.680 g (1.05 mmol) of 2,2′-CH₂-(4-Me-6-^(t)BuC₆H₂O)₂ZrCl₂(THF)₂ were mixed dry and dissolved in 30 ml of toluene. The solution was stirred for 4 days at room temperature, during which time it became yellow and turbid. The solvent was removed in a high vacuum and the residue was taken up in heptane. The MgCl₂(THF)₂ was filtered off, washed with heptane and the filtrate was evaporated to about 30 ml. After a few days at room temperature, yellow crystals formed. These were isolated by decantation and dried in a high vacuum. This gave 0.311 g (48%) of Me₂SiCp₂Zr(2,2′-CH₂-(4-Me-6-^(t)BuC₆H₂O)₂). Evaporation of the mother liquor and cooling to −30° C. gave, after a few days, a further 0.154 g (24%) of Me₂SiCp₂Zr(2,2′-CH₂-(4-Me-6-^(t)BuC₆H₂O)₂) by means of an identical work-up. Total yield: 72%

¹H-NMR chemical shifts in ppm (CD₂Cl₂, internal standard TMS, 298 K, 600 MHz)

Assignment 7.09 (d, 2H) ⁴J (1.3 Hz) C₆H₂ (H6) 6.92 (d, 2H) ⁴J (1.5 Hz) C₆H₂ (H4) 6.85 (t^(p), 2H) C₅H₄ 6.17 (t^(p), 2H) C₅H₄ 6.01 (t^(p), 2H) C₅H₄ 5.95 (t^(p), 2H) C₅H₄ 4.21 (d, 1H) ³J (13.8 Hz) CH₂ 3.11 (d, 1H) ³J (13.8 Hz) CH₂ 2.26 (s, 6H) CH₃ 1.41 (s, 18H) (CH₃)₃CH 0.811 (s, 6H) (CH₃)₂Si

Example 11

Preparation of Rac-Me₂Si(3-(2-Me-benz[e]indenyl)₂Zr(2,2′-(3-^(t)Bu-5-Me-C₆H₂O)₂)

17 mg (0.029 mmol) of Me₂Si(3-(2-Me-benz[e]indenyl)₂Mg(THF)₂ and 18.3 mg (0.0291 mmol) of 2,2′-(3-^(t)Bu-5-Me-C₆H₂O)₂ZrCl₂(THF)₂ were mixed dry in an NMR tube and dissolved in 0.5 ml of C₆D₆. After 6 days at room temperature, the solution is yellow and a new white precipitate has formed. An ¹H-NMR spectrum was recorded.

¹H-NMR chemical shifts in ppm (C₆D₆, internal standard TMS, 298 K, 250 MHz)

Assignment 8.63 (d) C₆H₄ or C₆H₂ 7.97 (d) C₆H₄ or C₆H₂ 7.78 (m) C₆H₄ or C₆H₂ 7.82 C₆H₄ or C₆H₂ 7.52 (m) C₆H₄ or C₆H₂ 7.35-7.03 (m) C₆H₄ or C₆H₂, C₆H₂ (phenoxy ligand) 6.97 (d) C₆H₂ (phenoxy ligand) 6.84 (s) C₅H 3.43 (sb) THF (free) 3.25 (s) CH₃ 2.27 (s) CH₃ (phenoxy ligand) 1.45 (m) THF (free) 1.23 (s) (CH₃)₃C 1.16 (s) (CH₃)₂Si

Example 12

Preparation of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂

5.21 g (13.81 mmol) of ZrCl₄(THF)₂ were suspended in 150 ml of toluene. At 0° C., 16 g (82.3 mmol) of Me₃SiO-2,6-(CH₃)₂-C₆H₃ were added thereto and the suspension was subsequently refluxed for 12 hours. The solvent was taken off and the residue was taken up in 80 ml of THF. This solution was covered with a layer of hexane. After some days at room temperature, colorless crystals were formed and these were isolated by decantation and dried in a high vacuum. This gave 1.82 g (3.31 mmol) of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂. Further concentration of the mother liquor and cooling to −30° C. gave, after identical isolation, a further 2.20 g (4.01 mmol) of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂.

Total yield: 4.02 g (7.32 mmol, 53%) of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂

Preparation of rac-C₂H₄(ind)₂Zr(O-2,6-Me₂C₆H₃)₂

15.7 mg (0.028 mmol) of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂ and 12.1 mg (0.028 mmol) of C₂H₄(ind)₂Mg(THF)₂ were mixed dry in an NMR tube and dissolved in 0.5 ml of C₆D₆. After 24 hours at room temperature, the solution had turned yellow and had become turbid due to precipitated MgCl₂(THF)₂. A ¹H-NMR spectrum was recorded and this found that only the racemic form of C₂H₄(ind)₂Zr-(O-2,4-Me₂C₆H₅)₂ had been formed.

¹H-NMR chemical shifts in ppm (C₆D₆, internal standard TMS, 298 K, 250 MHz)

Assignment 7.46 (d, 2H) C₆H₄ 7.02 (d, 2H) C₆H₄ 6.92 (d, 4H) C₆H₃ 6.82 (m, 4H) C₆H₃ or C₆H₄ 6.44 (tp, 2H) C₅H₄ 6.14 (d, 2H) C₅H₂ 5.94 (d, 2H) C₅H₂ 3.52 (m, 2H) C₂H₄ 3.17 (m, 2H) C₂H₄ 1.97 (s, 6H) CH₃

Example 13

Preparation of Rac-Me₂Si(ind)₂Zr(O-2,6-Me₂C₆H₃)₂

25 mg (0.045 mmol) of Me₂Si(ind)₂Mg(THF)₂ and 20.5 mg (0.045 mmol) of Cl₂Zr(O-2,6-Me₂C₆H₃)₂(THF)₂ were mixed dry in an NMR tube and dissolved in 0.5 ml of C₆D₆. After 24 hours at room temperature, the solution had turned yellow and had become turbid due to precipitated MgCl₂(THF)₂. A ¹H-NMR spectrum was recorded and this showed that only the racemic form of Me₂Si(ind)₂Zr(O-2,6-Me₂C₆H₃)₂ had been formed.

¹H-NMR chemical shifts in ppm (C₆D₆, internal standard TMS, 298 K, 250 MHZ).

Assignment 7.57 (d, 2H) C₆H₄ 7.20 (d, 2H) C₆H₄ 6.96-6.70 (m) C₆H₃ or C₆H₄ 6.47 (s, 4H) C₅H₂ 6.44 (tp, 2H) C₆H₄ 2.37-1.97 (m, 6H) CH₃ 0.81 (s, 6H) Me₂Si 

We claim:
 1. A process for preparing racemic metallocene complexes by reacting bridged or unbridged aromatic transition metal complexes of the formula I

where the substituents and indices have the following meanings: M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and the lanthanides, X are identical or different and are each fluorine, chlorine, bromine, iodine, hydrogen C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, —OR¹⁰ or —NR¹⁰R¹¹, n is an integer from 1 to 4, where n corresponds to the valence of M minus 2, R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms, R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms, R¹⁰, R¹¹ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹², where R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring, M¹ is silicon, germanium or tin and m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms, with cyclopentadienyl derivatives of alkali metals or alkaline earth metals and, if desired, subsequently replacing the bridged aromatic ligand or the two unbridged aromatic ligands.
 2. A process as claimed in claim 1, wherein R¹ and R⁸ in formula I are bulky substituents.
 3. A process as claimed in claim 1, wherein m in formula I is
 0. 4. A process as claimed in claim 1, wherein Y¹ are identical and are each oxygen.
 5. A process as claimed in claim 1, wherein cyclopentadienyl derivatives of magnesium are used.
 6. A racemic metallocene complex of the formula III

where the substituents and indices have the following meanings: M is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten or an element of transition group III of the Periodic Table and the lanthanides,

where: R¹, R⁸ are identical or different and are each fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, where the radicals mentioned may be partially or fully substituted by heteroatoms, R² to R⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, and adjacent radicals R² to R⁷ may form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms and the radicals mentioned may be fully or partially substituted by heteroatoms, Y, Y¹ are identical or different and are each

 ═BR¹², ═AlR¹², —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹², ═CO, ═PR¹² or ═P(O)R¹², where R¹² are identical or different and are each hydrogen, halogen, C₁-C₁₀-alkyl, C₁-C₁₀-fluoroalkyl, C₆-C₁₀-fluoroaryl, C₆-C₁₀-aryl, C₁-C₁₀-alkoxy, C₂-C₁₀-alkenyl, C₇-C₄₀-arylalkyl, C₈-C₄₀-arylalkenyl, C₇-C₄₀-alkylaryl, or two radicals R¹² together with the atoms connecting them form a ring, M¹ is silicon, germanium or tin and m is 0, 1, 2 or 3, or Y is non-bridging and is two radicals R′ and R″, where R′ and R″ are identical or different and are each hydrogen, fluorine, chlorine, bromine, iodine, C₁-C₂₀-alkyl, 3- to 8-membered cycloalkyl which in turn may bear a C₁-C₁₀-alkyl radical as substituent, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, Si(R⁹)₃ where R⁹ are identical or different and are each C₁-C₂₀-alkyl, C₃-C₁₀-cycloalkyl, C₆-C₁₅-aryl, or together with adjacent radicals R⁴ or R⁵ form saturated, partially saturated or unsaturated cyclic groups having from 4 to 15 carbon atoms, and the radicals mentioned can be fully or partially substituted by heteroatoms, R¹³ to R¹⁷ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R¹⁸)₃ where R¹⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

where the radicals R¹⁹ to R²³ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl which may in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl or arylalkyl, where adjacent radicals may together form cyclic groups having from 4 to 15 carbon atoms, or Si(R²⁴)₃ where R²⁴ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, or where the radicals R¹⁶ and Z together form a group —[T(R²⁵)(R²⁶)]_(q)—E—, where T can be identical or different and are each silicon, germanium, tin or carbon, R²⁵, R²⁶ are each hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl q is 1, 2, 3 or 4, E is

or A, where A is —O—,

where R²⁷ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl, alkylaryl or Si(R²⁸)₃ where R²⁸ are identical or different and are each C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl or alkylaryl.
 7. A racemic metallocene complex as claimed in claim 6, wherein R¹⁷ and R²³ are not hydrogen if R¹⁶ and Z together form a group —[T(R²⁵)(R²⁰)]_(q)—E—.
 8. A catalyst for the polymerization of olefinically unsaturated compounds or for stereoselective synthesis comprising racemic metallocene complexes of the formula III as claimed in claim
 6. 9. A process for polymerizing olefinically unsaturated compounds comprising polymerization in the presence of racemic metallocene complexes of the formula III as claimed in claim 6 as a catalyst or as a constituent of a catalyst system.
 10. A process for stereoselective synthesis comprising synthesis in the presence of racemic metallocene complexes of the formula III as claimed in claim 6 as a catalyst or as a constituent of a catalyst system. 